ASHINGTON, March 31 — House Democrats, backed by labor and organizations representing health care workers, blocked a plan today to create a compensation program for people disabled or killed by smallpox vaccine. Opponents said the Bush administration's proposal was inadequate.

The proposal was intended to encourage emergency workers around the nation to be inoculated against smallpox by offering $262,100 if a person died or was totally disabled by the vaccine and up to that amount for lost wages over a lifetime. With the number of inoculations running far below expectations and the administration warning of terrorist attacks involving smallpox, sponsors of the measure said it was urgently needed.

"We don't have time to quibble about what is enough here," said Representative Billy Tauzin, the Louisiana Republican who is chairman of the Energy and Commerce Committee.

To speed its passage, Republican leaders of the House brought the measure up under a process usually reserved for noncontroversial bills, one that would have required a two-thirds majority to pass it. But the measure failed on a straight majority vote of 206 to 184.

Democrats said the measure was not generous enough, and they wanted to remove the cap on lost wages. They also said a requirement that workers be vaccinated within 180 days of the start of the program or forfeit their right to compensation amounted to coercion.

"The president wants our first responders to be prepared for smallpox," said Representative Lois Capps, a California Democrat who is a registered nurse. "We want to help. But this bill and efforts to block alternatives are simply making our nurses, firefighters and other first responders more uncomfortable."

When the administration announced the vaccinations last year, the hope was that about 500,000 health and emergency workers would volunteer. But lawmakers said only about 25,000 had done so. Three people suffered heart attacks soon after being vaccinated, though it is unclear whether the vaccine was the cause. Some states have suspended their programs.

Republicans said they might try to bring the measure back for a vote later this week or include it in an emergency spending bill being written to pay for the war in Iraq and domestic security measures. Democrats said it would be "self-defeating" to bring back the proposal without changes because opposition to the plan was growing.